Baloo and Milou on the KDE desktop is often decried for performance reasons, but is quite powerful. I like how it can perform full-text search in my documents

Baloo and Milou on the KDE desktop is often decried for performance reasons, but is quite powerful. I like how it can perform full-text search in my documents (pdf, etc). It also searches your e-mails if you use Kmail (and contacts, events, etc if you use other KDE PIM tools). I only wish it was a bit less eager to extract files on underpowered laptops, and it would be nice if it could OCR pdfs and tag images (facial recognition, etc).